Recently, various organic phosphate and phosphonate complexes of technetium-99m have been suggested as gamma-emitting radionuclide agents for skeletal imaging. The excellent physical characteristics (half-life of 6 hours and monoenergetic gamma emission of 140 KeV with an external photon yield of 90%) of the readily available radionuclide technetium-99m render it an attractive substitute for the conventionally employed long-lived nuclide strontium 85 (half-life 65 days) and the inconveniently short-lived fluorine 18 (half-life 1.83 hours). By virtue of its optimum half-life characteristics and absence of beta emission, technetium-99m can be administered in relatively large doses (10-15 mCi) without exceeding reasonable radiation levels.
Until fairly recently, technetium-99m has been used almost exclusively in radioisotopic imaging procedures for almost every major organ in man with the exception of the skeleton. Recently, however, various organic phosphate and phosphonate complexes of technetium-99m have been employed for skeletal imaging purposes. (Perez et al., J. Nucl. Med. 13:788-789, 1972; Subramanian et al., Radiology, 98:192-196, 1971; Subramanian et al., Radiology, 102:701-704, 1972; Subramanian et al., J. Nucl. Med., 13:947-950, 1972; Tofe et al., J. Nucl. Med., 15:69-74, 1974; Yano, J. Nucl. Med. 14:73-78, 1973; Castronova et al., J. Nucl. Med. 13:823-827, 1972; and Subramanian et al., J. Nucl. Med., August, 1975 (U.S. application Ser. No. 368,473, filed June 11, 1973).
It was found that when solutions of these technetium-99m phosphate and phosphonate complexes are given intravenously, the technetium-99m localizes to a great extent in bone, particularly in diseased or abnormal areas of the skeleton. Good visualization of both normal bone and skeleton lesions is observed about 2 hours after administration of the complexes. Normal and abnormal skeletal tissues are readily delineated using conventional radioisotope imaging devices such as rectilinear scanners or scintillation cameras.
There has been a continuing search in this area for technetium-99m complexes having a higher bone uptake than those currently employed in the art.